GB 4789.28-2024 PDF English
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| Standard ID | Contents [version] | USD | STEP2 | [PDF] delivery | Name of Chinese Standard | Status |
| GB 4789.28-2024 | English | 935 |
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National food safety standard - Food Microbiology Testing - Quality Requirements for Medium and Reagents
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| GB 4789.28-2013 | English | 155 |
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National food safety standard - Food Microbiological Examination - Quality requirements of culture media and reagents
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| GB/T 4789.28-2003 | English | RFQ |
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Microbiological examination of food hygiene -- Staining methods, culture mediums and reagents
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| GB 4789.28-1994 | English | RFQ |
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Microbiological examination of food hygiene. Stainning methods, culture mediums and reagents
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| GB 4789.28-1984 | English | RFQ |
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Microbiological examination of food hygiene--Staining methods, culture mediums and reagents
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GB 4789.28-2024: National food safety standard - Food Microbiology Testing - Quality Requirements for Medium and Reagents
---This is an excerpt. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.), auto-downloaded/delivered in 9 seconds, can be purchased online: https://www.ChineseStandard.net/PDF.aspx/GB4789.28-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
National food safety standards - Food microbiology testing -
Quality requirements for medium and reagents
Issued on. FEBRUARY 08, 2024
Implemented on. AUGUST 08, 2024
Issued by. National Health Commission of PRC;
State Administration for market Regulation.
Table of Contents
Foreword... 4
1 Scope... 5
2 Terms and definitions... 5
3 Quality assurance of culture media and reagents... 10
4 Preservation and use of test strains... 15
5 Quality requirements for culture media and reagents... 16
6 Test methods of media and reagent performance... 18
Appendix A Flow chart for media performance testing method... 28
Appendix B Analysis of quality problems and reasons caused by incorrect preparation
of culture medium... 32
Appendix C Preparation of standard reserve strains and working strains... 34
Appendix D Medium components specified in food safety microbiological inspection
standards... 36
Appendix E Quality control criteria for reference media in food safety microbiological
inspection standards... 38
Appendix F Quality control criteria for culture media and reagents used in food
microbiology laboratories... 44
Appendix G Test strain... 96
Appendix H Spiral plate method... 99
1 Scope
This standard specifies the quality requirements for culture media and reagents used in
food microbiology testing.
This standard applies to the quality control of culture media and reagents for food
microbiology testing.
2 Terms and definitions
2.1 Quality control
Technical operations and activities undertaken to meet quality requirements.
2.2 Lots of media and reagents
The complete traceability unit of culture media and reagents, which refers to a
certain number of products produced in a specific production cycle and meeting
production quality requirements. These products have the same batch number.
2.3 Performance of media and reagents
The reaction of culture media and reagents to the test strain under certain conditions.
2.4 Culture medium
Substances in liquid, semi-solid or solid form, containing natural or synthetic
ingredients, used to ensure the reproduction, identification or maintenance of vitality
of microorganisms.
2.5 Liquid culture medium
A culture medium consisting of an aqueous solution containing one or more
components (e.g. buffered peptone water).
2.6 Solid media
A culture media, which is formed by adding certain amount of solidified material
(such as agar) to the liquid culture medium, after boiling or moist heat sterilization,
cooled to room temperature and solidified.
Solid culture medium poured into a petri dish is generally called a "plate"; solid
culture medium poured into a test tube and placed at an angle is often called a "slant",
when the culture medium solidifies.
2.7 Semi-solid medium
A culture media, which is formed by adding a small amount of solidified matter
(such as agar) to the liquid culture medium, after boiling or moist heat sterilization,
semi-solidified after cooling.
2.8 Transport media
A culture medium, that protects and maintains microbial activity after sampling and
before laboratory processing, AND does not allow obvious proliferation or reduction
of microorganisms.
The transport medium usually does not contain substances that allow
microorganisms to proliferate, but the medium shall protect the strains (e.g.,
buffered glycerol-sodium chloride solution transport medium).
3 Quality assurance of culture media and reagents
3.1 Supporting documents
3.1.1 Documents provided by the manufacturer
The manufacturer shall provide the following information (electronic text can be
provided).
3.1.2 Product handover acceptance
3.2 Storage
3.2.1 General requirements
Culture media and reagents shall be stored and used, in strict accordance with the
storage conditions, expiration date, usage methods provided by the supplier.
3.2.2 Commercial dehydrated synthetic culture medium and its additives
Acceptance shall include the following.
3.2.3 Commercial ready-to-use media and reagents
It shall be stored and used, in strict accordance with the storage conditions, validity
period, usage methods provided by the supplier.
3.2.4 Laboratory-made media
Store it under conditions that ensure that its ingredients will not change, that is, avoid
light and dry storage. If necessary, store it in a refrigerator at 2 °C ~ 8 °C. It is usually
recommended that the storage period of plates shall not exceed 4 weeks; the storage
period of bottled and test tube media shall not exceed 6 months.
If it needs to add unstable additives to the culture medium, they shall be prepared and
used immediately. The solid culture media containing active chemicals or unstable
components shall also be prepared and used immediately, which shall not be melted
twice.
3.3 Laboratory preparation of culture media
3.3.1 General requirements
The correct preparation of culture media is one of the most basic steps in
microbiological testing. When using dehydrated culture media and other ingredients,
especially those containing toxic and harmful substances (such as bile salts or other
selective agents), good laboratory practices and instructions for use provided by
manufacturers shall be followed. Improper preparation of culture medium can lead to
quality problems in the culture medium (see Appendix B).
When using commercial dehydrated synthetic medium to prepare culture medium, the
preparation shall be strictly in accordance with the instructions provided by the
manufacturer, such as mass (volume), pH, preparation date, sterilization conditions,
operating procedures, etc.
3.3.2 Water
The conductivity of the test water shall not exceed 25 µS/cm (equivalent to resistivity
≥ 0.04 MΩ/cm) at 25 °C, unless otherwise specified.
The microbial contamination of test water shall not exceed 103 CFU/mL. Microbial
contamination levels shall be checked regularly according to GB 4789.2.
3.4 Use of culture medium
3.4.1 Melting of agar medium
Melt the culture medium by placing it in a boiling water bath or using an equivalent
method (such as laminar steam in a pressure cooker). Media after high-pressure
treatment shall be reheated to a minimum. The melted culture medium is placed in a
constant temperature device, at 47 °C ~ 50 °C, for cooling and insulation (the
temperature of the constant temperature device can be appropriately increased,
according to the actual culture medium solidification temperature) until use. The time
for the culture medium to reach 47 °C ~ 50 °C is related to the variety, volume, quantity
of the culture medium. The melted culture medium shall be used as soon as possible
and shall not be left for more than 4 hours. Unused culture medium cannot be re-
solidified for next use.
4 Preservation and use of test strains
4.1 General requirements
In order to successfully preserve and use strains, different preservation methods shall
be used for different strains. It can choose to use freeze-drying preservation, ultra-low
temperature (not higher than -70 °C) freezing preservation, liquid nitrogen preservation
or other effective preservation methods.
4.2 Commercially sourced test strains
For original packaged test strains obtained from a standard strain preservation center or
other validly certified commercial agency, recovery and use shall be carried out in
accordance with the instructions provided by the manufacturer.
4.3 Standard stock strains prepared in the laboratory
When storing and using the standard reserve strain, which is used for performance
testing (see Figure C.1 in Appendix C), care shall be taken to avoid cross-contamination
and reduce strain mutations or typical characteristic changes. It shall prepare multiple
copies of the standard reserve strain; it shall be stored at ultra-low temperature (not
higher than -70 °C) or in freeze-dried form. Storage times at higher temperatures shall
be shortened.
4.4 Reserve strains
Reserve strains are usually prepared from standard reserve strains that are freeze-dried
or cryopreserved (see Figure C.2).
4.5 Working strains
Working strains are prepared from standard reserve strains or reserve strains.
Working strains cannot be used to make standard strains, standard reserve strains, or
reserve strains.
5 Quality requirements for culture media and reagents
5.1 Basic requirements
5.1.1 Culture media and reagents
The quality of culture media and reagents is determined by factors such as the quality
of the basic ingredients, control of the preparation process, elimination of microbial
contamination, packaging and storage conditions.
Suppliers or preparers shall control the quality of basic ingredients, preparation
processes, elimination of microbial contamination, packaging and storage conditions,
to ensure that the physical and chemical properties of culture media and reagents meet
the requirements of relevant standards.
Various components, additives or selective agents of culture media and reagents shall
be appropriately evaluated for quality.
Culture media and reagents not described in Appendix F shall be quality controlled,
according to the following requirements.
5.1.2 Basic ingredients
The media components listed in national standards can usually be used directly. Due to
quality differences in some of the components used to prepare the culture medium (see
Appendix D), appropriate adjustments to their dosage may be allowed, such as.
5.2 Microbiological requirements
5.2.1 Introduction
The culture medium and reagents shall meet the requirements of quality control criteria
in Appendix F; their performance testing methods shall be implemented in accordance
with Chapter 6.When the laboratory uses commercial culture media and reagents, the
information provided by the manufacturer in accordance with 3.1.1 shall be retained
and acceptance procedures shall be established. If the manufacturer can provide
corresponding inspection capabilities and obtain an inspection report for the same batch
of products issued by the relevant national certification and accreditation qualification
inspection agency, the laboratory can retain the relevant certification documents and
conduct repeated tests on the performance of the batch of culture media, based on actual
needs. (Medium and reagents not included in Appendix F can be tested based on the
performance of the culture medium and reagents, by referring to the method established
in Appendix F).
5.2.2 Growth characteristics
6 Test methods of media and reagent performance
6.1 Quantitative test method for non-selective isolation and
enumeration of target bacterial growth rate in solid culture media
6.2 Test methods for selective isolation and enumeration of solid media
6.2.1 Quantitative test method for target bacterial growth rate
6.2.2 (Selective) semi-quantitative testing method for non-target bacteria
6.2.3 Qualitative testing methods for non-target bacteria (specificity)
6.3 Semi-quantitative test method for non-selective enrichment media
6.4 Semi-quantitative testing method for selective enrichment media
6.4.1 Preparation of culture medium
Divide the culture medium into test tubes, 10 mL per tube.
6.4.2 Preparation of working bacterial suspension
Follow the requirements in 6.1.1.
6.4.3 Inoculation
6.4.4 Inoculation of culture medium
6.5 Semi-quantitative test method for selective liquid enumeration
media
6.5.1 Preparation of culture medium
Divide the culture medium into test tubes, 10 mL per tube.
6.5.2 Preparation of working bacterial suspension
Follow the requirements in 6.3.2.
6.5.3 Inoculation
6.5.4 Interpretation of results
Use visual turbidity values (e.g. 0 ~ 2) to evaluate culture media.
6.6 Quantitative test methods for suspension media and transport
media
6.7 Qualification media test methods
6.7.1 Liquid culture medium
6.7.2 Semi-solid media
6.7.2.1 Preparation of culture medium
Divide culture medium into test tubes. After sterilization, place it upright and cool
before use.
6.7.2.2 Inoculation
Take fresh test strains, use an inoculation needle to pick out the bacterial lawn and
inoculate it into the culture medium to be tested. Incubate according to the incubation
time and temperature specified in the standard method.
6.7.2.3 Observation and interpretation of results
For tests that require the addition of indicators, when the microorganisms are growing
well, add the indicators in order and then observe the results. For interpretation of
results, refer to Table F.7.
6.7.3 High-level slant medium and slant medium
6.7.4 Plate culture medium
6.8 Test methods for experimental reagent
6.8.1 Test methods
Follow the reagent instructions.
6.8.2 Observation and interpretation of results
Refer to Table F.7.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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